QPixmap *pix;//设置画图背景
QPoint start;//鼠标按下时的坐标
QPoint end;//鼠标抬起时的坐标
int status;//画图状态，1：直线，2：矩形，3：椭圆，4：自由绘图
QPen pen;//设置线条的属性
QBrush brush;//设置填充属性

protected:
    void mousePressEvent(QMouseEvent *event);//鼠标按下事件
    void mouseMoveEvent(QMouseEvent *event);//鼠标移动事件
    void mouseReleaseEvent(QMouseEvent *);//鼠标释放事件
    void paintEvent(QPaintEvent*);//绘画事件

void paint::mousePressEvent(QMouseEvent *event)
{
    start=event->pos();//获得鼠标点击坐标

}
void paint::mouseReleaseEvent(QMouseEvent *event)
{
    end=event->pos();
    qDebug()<<start<<endl<<end<<endl;
    QPainter *painter=new QPainter(pix);
    painter->setPen(pen);//设置线条属性
    painter->setBrush(brush);//设置笔刷属性
    switch (status) {
    case 1://画直线
    {
        painter->drawLine(start,end);
        break;
    }
    case 2://画矩形
    {

        int width=end.x()-start.x();
        int height=end.y()-start.x();
        painter->drawRect(start.x(),start.y(),width,height);
        break;

    }
    case 3://画椭圆
    {
        int width=end.x()-start.x();
        int height=end.y()-start.x();
        painter->drawEllipse(start.x(),start.y(),width,height);
        break;
    }
    }
    this->update();
    delete painter;

}
void paint::paintEvent(QPaintEvent *)
{

  QPainter painter(this);
  painter.drawPixmap(QPoint(0, 0), *pix);


}
void paint:: mouseMoveEvent(QMouseEvent *event)
{
    if(status==4)//绘制鼠标移动轨迹
    {
        QPainter* painter=new QPainter(pix);
        end=event->pos();
        painter->setPen(pen);
        painter->drawLine(start,end);//每一次移动画直线
        this->update();
        start=end;//下一次绘制的开始点是这次的结束点
        delete painter;//若无delete则只可以绘制一次

    }
}

paint::paint(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::paint)
{
    ui->setupUi(this);
    
    //设置画布
    pix=new QPixmap(this->size()*5);
    pix->fill(Qt::white);
    
    //设置初使属性
    brush.setColor(Qt::NoBrush);
    status=1;
    
    //连接信号和槽
    connect(ui->line,SIGNAL(triggered(bool)),this,SLOT(status_line()));
    connect(ui->rect,SIGNAL(triggered(bool)),this,SLOT(status_rect()));
    connect(ui->ellipse,SIGNAL(triggered(bool)),this,SLOT(status_ellipse()));
    connect(ui->actionfree,SIGNAL(triggered(bool)),this,SLOT(status_free()));
    connect(ui->actionred,SIGNAL(triggered(bool)),this,SLOT(change_color_red()));
    connect(ui->actionblue,SIGNAL(triggered(bool)),this,SLOT(change_color_blue()));
    connect(ui->actiongreen,SIGNAL(triggered(bool)),this,SLOT(change_color_green()));
    connect(ui->actionblack,SIGNAL(triggered(bool)),this,SLOT(change_color_black()));
    connect(ui->action2,SIGNAL(triggered(bool)),this,SLOT(penwidth2()));
    connect(ui->action5,SIGNAL(triggered(bool)),this,SLOT(penwidth5()));
    connect(ui->action8,SIGNAL(triggered(bool)),this,SLOT(penwidth8()));
    connect(ui->action10,SIGNAL(triggered(bool)),this,SLOT(penwidth10()));
    connect(ui->solid_line,SIGNAL(triggered(bool)),this,SLOT(set_solid()));
    connect(ui->dash_line,SIGNAL(triggered(bool)),this,SLOT(set_dash()));
    connect(ui->dash_dot,SIGNAL(triggered(bool)),this,SLOT(set_dashdot()));
    connect(ui->dash_dot_dot,SIGNAL(triggered(bool)),this,SLOT(set_dashdotdot()));
    connect(ui->dot_line,SIGNAL(triggered(bool)),this,SLOT(set_dot()));
    connect(ui->fred,SIGNAL(triggered(bool)),this,SLOT(set_fill_red()));
    connect(ui->fblue,SIGNAL(triggered(bool)),this,SLOT(set_fill_blue()));
    connect(ui->fblack,SIGNAL(triggered(bool)),this,SLOT(set_fill_black()));
    connect(ui->fgreen,SIGNAL(triggered(bool)),this,SLOT(set_fill_green()));
    connect(ui->solid_pattern,SIGNAL(triggered(bool)),this,SLOT(set_solid_pattern()));
    connect(ui->dense_pattern,SIGNAL(triggered(bool)),this,SLOT(set_dense_pattern()));
    connect(ui->none,SIGNAL(triggered(bool)),this,SLOT(set_none_pattern()));
}

public slots:
    //设置绘制形状
    void status_line();
    void status_rect();
    void status_ellipse();
    void status_free();//绘制鼠标轨迹
    //设置线条颜色
    void change_color_blue();
    void change_color_red();
    void change_color_green();
    void change_color_black();
    //设置线条宽度
    void penwidth2();
    void penwidth5();
    void penwidth8();
    void penwidth10();
    //设置线条样式
    void set_solid();
    void set_dash();
    void set_dot();
    void set_dashdot();
    void set_dashdotdot();
    //设置填充颜色
    void set_fill_red();
    void set_fill_blue();
    void set_fill_green();
    void set_fill_black();
    //设置填充样式
    void set_solid_pattern();
    void set_dense_pattern();
    void set_none_pattern();

void paint::status_line()
{
    status=1;
}

void paint::change_color_red()
{
    pen.setColor(Qt::red);
    //注意书写格式，不可以写为pen.setColor("red");否则无法传入颜色
}

void paint::penwidth5()
{
    pen.setWidth(5);
}

void paint::set_dash()
{
    pen.setStyle(Qt::DashLine);
}

void paint::set_fill_blue()
{
    brush.setColor(Qt::blue);
}

void paint::set_dense_pattern()
{
    brush.setStyle(Qt::Dense7Pattern);
}

void paint::set_none_pattern()
{
    brush.setStyle(Qt::NoBrush);
}